Martin O'Halloran

• Ollscoil na Gaillimhe – University of Galway

Adrenocortical carcinoma (ACC) is a rare malignancy of the adrenal cortex that is associated with a poor prognosis. Developing effective treatment options for ACC is challenging owing to the current lack of representative pre-clinical models. This study addressed this limitation by developing and characterising 3D cell cultures incorporating the AC...

An abdominal aortic aneurysm (AAA) is a dilation of the aorta over its normal diameter (> 3 cm). The minimally invasive treatment adopted uses a stent graft to be deployed into the aneurysm by a catheter to flow blood through it. However, this approach demands frequent monitoring using imaging modalities that involve radiation and contrast agents....

Disclosure: R. Challapalli: None. A. Sorushanova: None. C. Hong: None. N.J. Mullen: None. S. Feely: None. O. Covarrubias-Zambrano: None. J. Covarrubias: None. S. Varghese: None. C. Hantel: None. P. Owens: None. M. O’Halloran: None. P. Prakash: None. S.H. Bossmann: None. M.C. Dennedy: None. Adrenocortical carcinoma (ACC), a rare malignancy with a po...

Adrenal gland-induced hypertension results from underlying adrenal gland disorders including Conn’s syndrome, Cushing's syndrome, and Pheochromocytoma. These adrenal disorders are a risk for cardiovascular and renal morbidity and mortality. Clinically, treatment for adrenal gland-induced hypertension involves a pharmaceutical or surgical approach....

Over the past two decades, there has been extensive research into surveillance methods for the post-endovascular repair of abdominal aortic aneurysms, highlighting the importance of these technologies in supplementing or even replacing conventional image-screening modalities. This review aims to provide an overview of the current status of alternat...

Birth asphyxia is a potential cause of death that is also associated with acute and chronic morbidities. The traditional and immediate approach for monitoring birth asphyxia (i.e., arterial blood gas analysis) is highly invasive and intermittent. Additionally, alternative noninvasive approaches such as pulse oximeters can be problematic, due to the...

Abdominal aortic aneurysm (AAA) is a dilation of the aorta artery larger than its normal diameter (>3 cm). Endovascular aneurysm repair (EVAR) is a minimally invasive treatment option that involves the placement of a graft in the aneurysmal portion of the aorta artery. This treatment requires multiple follow-ups with medical imaging, which is expen...

Microwave thermal ablation is an established therapeutic technique for treating malignant tissue in various organs. Its success greatly depends on the knowledge of dielectric properties of the targeted tissue and on how they change during the treatment. Innovation in lung navigation has recently increased the clinical interest in the transbronchial...

Intrapartum foetal hypoxia is related to long-term morbidity and mortality of the foetus and the mother. Foetal surveillance is extremely important to minimize the adverse outcomes arising from foetal hypoxia during labour. Several methods have been used in current clinical practice to monitor foetal well-being. For instance, biophysical technologi...

Microwave Tomography (MWT) is emerging as a potential imaging technique for monitoring bone health due to its ability to determine the dielectric properties of tissues under investigation. Studies have demonstrated a significant dielectric contrast between healthy and diseased human trabecular bones, which suggests that MWT has the potential to det...

The evaluation and characterization of microwave imaging (MWI) prototype along with the optimization of imaging algorithm is a precursor step before the clinical study to measure in vivo dielectric properties. This study presents the microwave tomographic (MWT) image reconstruction of anthropomorphic calcaneus phantoms by using a specialized micr...

Adrenal gland-induced hypertension, also known as secondary hypertension, is a medical condition caused by an underlying adrenal pathology, most typically adrenocortical adenomas. Current clinical practices involve pharmacotherapy or surgical resection to treat adrenal gland diseases that cause hypertension. However, due to the limitations of these...

Cardiac catheter ablation (CCA) is a common method used to correct cardiac arrhythmia. Pulsed Field Ablation (PFA) is a recently-adapted CCA technology whose ablation is dependent on electrode and waveform parameters (factors). In this work, the use of the Design of Experiments (DoE) methodology is investigated for the design and optimization of a...

Asphyxia, a leading cause of illness and death in newborns, can be improved by early detection and management. Arterial blood gas (ABG) analysis is commonly used to diagnose and manage asphyxia, but it is invasive and carries risks. Dermal interstitial fluid (ISF) is an alternative physiological fluid that can provide valuable information about a p...

For conductivity measurements, the sensing volume is determined by the electrode size and geometry and can significantly confound results, particularly in smaller samples. In this study, we investigate the influence of the sensing volume on conductivity measurements. Two distinct four-electrode probes are used to measure the conductance of a 0.1 mo...

This paper presents a miniaturized four-electrode probe for measuring the conductivity of biological tissues at radio frequencies. The probe was developed to address two common challenges in tissue conductivity measurements at radio frequencies: the limited size of the sample compared to the sensing volume of the probe and the electrode polarizatio...

Atrial fibrillation is the most common type of cardiac arrhythmias in humans, mostly caused by hyper excitation of specific areas in the atrium resulting in dyssynchronous atrial contractions, leading to severe consequences such as heart failure and stroke. Current therapeutics aim to target this condition through both pharmacological and non-pharm...

Simple Summary Our study provides the first accurate dielectric characterisation of human lung tumours and parenchyma. Data were collected from neoplastic and non-neoplastic pulmonary tissue in the microwave frequency range prior to scheduled pathology analysis. On average, values from pulmonary tumours were found to be twice the value of normal lu...

Objectives To develop and assess a system for shared ventilation using clinically available components to individualize tidal volumes. Design Evaluation and in vitro validation study Setting Ventilator shortage during the SARS-CoV-2 pandemic. Participants The team consisted of physicians, bioengineers, computer programmers, and medical technolog...

Bio-impedance measurements require properly designed and characterised probes. Particular attention must be paid to the excitation signals and temperature compensation to meet the requirements of the linear sample response and the measurement accuracy. Here, we propose a reliable method to characterise probe performance for conductivity measurement...

Primary Aldosteronism is the most common cause of secondary hypertension. First-line treatment; adrenalectomy resects adrenal nodules and adjacent normal tissue, limiting suitability to those who present with unilateral disease. Use of thermal ablation represents an emerging approach as a possible minimally invasive therapy for unilateral and bilat...

Knowledge of dielectric properties of lung tissue is fundamental for the improvement of lung disease diagnostics and therapeutic solutions (e.g. microwave imaging and microwave thermal ablation treatment). Although lung disease rates are increasing, lung tissue remains one of the least characterized tissues due to its heterogeneity, variability in...

Recent studies have shown that ablation techniques have the potential to eradicate adrenal adenomas while preserving the functionalities of the adrenal gland and the surrounding anatomical structures. This study explores a new microwave ablation (MWA) approach operating at 5.8 GHz and using anatomical and dielectric characteristics of the target ti...

Background and objectives: Pulsed Electric Field (PEF) ablation has been proposed as a non-thermal energy to treat atrial fibrillation (AF) by epicardial ablation of ganglionated plexi (GP), which are embedded within epicardial fat. Our objective was to study the distribution of the electric field through the involved tissues (fat, GPs, myocardium...

Introduction Primary Aldosteronism is the most common cause of secondary hypertension. First-line treatment; adrenalectomy resects adrenal nodules and adjacent normal tissue, limiting suitability to those who present with unilateral disease. Use of thermal ablation represents an emerging approach as a possible minimally invasive therapy for unilate...

Primary aldosteronism (PA) is the principal cause of secondary hypertension and accounts for 5-12% of all hypertension. PA is characterized by unregulated aldosterone secretion from unilateral or bilateral nodules on the adrenal glands. High levels of aldosterone are associated with an increased risk of cardiovascular and cerebrovascular complicati...

Purpose To assess the feasibility of delivering microwave ablation for targeted treatment of aldosterone producing adenomas using image-based computational models. Methods We curated an anonymized dataset of diagnostic ¹¹C-metomidate PET/CT images of 14 patients with aldosterone producing adenomas (APA). A semi-automated approach was developed to...

The electrical properties of many biological tissues are freely available from the INRC and the IT’IS databases. However, particularly in lower frequency ranges, few studies have investigated the optimal measurement protocol or the key confounders that need to be controlled, monitored, and reported. However, preliminary work suggests that the conta...

Background and objectives Adrenocortical neoplasms are the main causes of secondary hypertension and related comorbidities including hypokalemia and cardiovascular diseases. Conventional techniques for the management of this condition are often invasive and not resolutive. Recent studies proposed microwave thermal ablation (MWA) to eradicate adreno...

Background: Irreversible electroporation has emerged as a new modality to overcome issues associated with other energy sources for cardiac ablation. Strong evidence on the optimal, effective, and selective voltage threshold is lacking for both in-vitro and pre-clinical in-vivo studies. The aim of this study is to examine the optimal threshold for...

Cardiac ablation with irreversible electroporation (IRE) is quickly being established as a modality of choice for atrial fibrillation treatment. While it has not yet been optimised, IRE has the potential to significantly limit collateral damage and improve cell-specific targeting associated with other energy sources. However, more tissue and cell-s...

Birth asphyxia a potential cause of death is also associated with acute, and chronic morbidities. The traditional and immediate approach to monitor birth asphyxia (i.e., arterial blood gas analysis) is highly invasive and intermittent. Additionally, alternative non-invasive approaches such as pulse oximeter can be problematic, due to the possibilit...

Background: Postoperative surgical adhesions constitute a major health burden internationally. A wide range of materials have been evaluated, but despite constructive efforts and the obvious necessity, there remains no specific barrier widely utilized to prevent postoperative adhesion formation. The aim of this study was to highlight and character...

Background and objectives Pulsed Electric Field (PEF) ablation has been proposed as a non-thermal energy to treat atrial fibrillation (AF) by ablation of ganglionated plexi using the epicardial approach. The electric field distribution at the target site (heart) and its surroundings has not yet been assessed previously, using epicardial ablation te...

Purpose Bio-effects following thermal treatments are a function of the achieved temperature profile in tissue, which can be estimated across tumor volumes with real-time MRI thermometry (MRIT). Here, we report on expansion of a previously developed small-animal microwave hyperthermia system integrated with MRIT for delivering thermal ablation to su...

Cardiovascular disease is the leading cause of premature death globally. There is emerging evidence that the morphology and composition of atherosclerotic plaques are a more reliable predictor of acute plaque events than the degree of coronary stenosis. The currently used plaque diagnostic methods - x-ray angiography, computed coronary tomography...

The evaluation of the microwave imaging (MWI) prototype and imaging algorithms on experimental bone phantoms is a precursor step before clinical testing for measuring in vivo dielectric properties of human bones. To this end, this paper presents microwave tomographic image reconstruction of experimental phantoms of normal and diseased human calca...

Recently, non-thermal pulsed-field-ablation using electroporation has generated a lot of interest as a potential treatment for Atrial Fibrillation. The electrical properties, and specially the conductivity of cardiac tissues, are used in the in treatment planning of non-thermal pulsed field ablation. However, there is no standard approach to measur...

In this study we measured the electrical conductivity of bovine liver. The measurements were performed at frequencies from 10 Hz to 10 kHz (N=5 frequencies) using a custom four-electrode probe and a galvanostat. We examined how the pressure applied between the probe and the tissue influenced the conductivity of the tissue. We performed measurements...

Achieving a better characterization of human blood conductivity is of high relevance for medical applications. In this study we measured the complex impedance of N = 10 human whole blood samples (from N = 10 oncology patients) at room temperature (T = 22.6 $\pm\; 0.8\;^\circ \mathrm{C}$ ) and at body temperature (T = 36.6 $\pm\; 0.4\;^\circ \mat...

Microwave breast imaging has seen increasing use in clinical investigations in the past decade with over eight systems having being trialled with patients. The majority of systems use radar-based algorithms to reconstruct the image shown to the clinician which requires an estimate of the dielectric properties of the breast to synthetically focus si...

Aims: Irreversible electroporation is an ablation technique being adapted for the treatment of atrial fibrillation. Currently, there are many differences reported in the in vitro and pre-clinical literature for the effective voltage threshold for ablation. The aim of this study is a direct comparison of different cell types within the cardiovascul...

The introduction of lung navigation systems in the clinical practice has enabled a transbronchial minimally invasive access to flexible microwave ablation catheters for the treatment of lung cancer lesions. These complex procedures are currently performed under Cone-Beam CT and require lung navigation system and bronchoscope. On bench lung models i...

Rationale & Objective Adaptive design methods are intended to improve efficiency of clinical trials and are relevant to evaluating interventions in dialysis populations. We sought to determine the use of adaptive designs in dialysis clinical trials and quantify trends in their use over time. Study Design We completed a novel full text systematic r...

This paper presents impedance measurements of the left atrium appendage using a tetrapolar probe from 0.1 Hz to 100 kHz. The results show that the conductivity of the left atrium appendage averages around 2.5 mS/cm, aligning with conductivities of cardiac muscle in the literature.

Targeted cellular ablation is being increasingly used in the treatment of arrhythmias and structural heart disease. Catheter-based ablation for atrial fibrillation (AF) is considered a safe and effective approach for patients who are medication refractory. Electroporation (EPo) employs electrical energy to disrupt cell membranes which has a minimal...

In this paper, we examined how the applied pressure influences the measurement of conductivity in lung tissue. We found that the conductivity of lung increases with increased pressure. The increase in conductivity can be explained by the air being pushed out of the lung under the applied pressure.

Background and Aims Adaptive design methods are intended to improve efficiency of clinical trials, and relevant to evaluating interventions in dialysis populations. We sought to quantify the use of adaptive design clinical trials in dialysis. Method We completed a full text systematic review and adhered to the Preferred Reporting Items for Systema...

Introduction: Primary Aldosteronism (PA) is the commonest secondary cause of hypertension. Mainstay therapy, adrenalectomy resects both hypersecreting and adjacent normal tissue. It is therefore only suitable for patients with unilateral disease (40% cases), whom are surgical candidates. Thermal therapy presents a plausible minimally invasive thera...

The dielectric properties of bones are found to be influenced by the demineralisation of bones. Therefore, microwave imaging (MWI) can be used to monitor in vivo dielectric properties of human bones and hence aid in the monitoring of osteoporosis. This paper presents the feasibility analysis of the MWI device for monitoring osteoporosis. Firstly, t...

Electrical conductivity of blood at low frequencies is fundamental for medical electromagnetic applications, such as pulsed field ablation of cardiac tissue. There are several studies in the literature reporting conductivity measurements of blood. However, knowledge of this data at frequencies below 100 kHz is limited due to measurement challenges,...

Accurate knowledge of the dielectric properties of biological tissues is important in dosimetry studies and for medical diagnostic, monitoring and therapeutic technologies. In particular, the dielectric properties of the heart are used in numerical simulations of radiofrequency and microwave heart ablation. In one recent study, it was demonstrated...

Many similarities exist between ultrasound and microwave imaging, however, ultrasound is typically performed with a handheld transducer whereas antennas are placed around the subject of imaging for microwave breast imaging. Hence, ultrasound beamformers are not always directly applicable for microwave imaging. Signals traverse different paths exper...

Historically, adrenal glands diseases causing hypertension, such as Primary Aldosteronism (PA), have been treated through pharmacotherapy or surgical resection. Given the shortcomings of the available treatment options, the interest in alternative and less invasive treatment modalities such as microwave ablation (MWA), has increased. In order to de...

Thermal ablative techniques have been used in kidney tumour treatments; these treatments use electromagnetic energy to increase the temperature of the target tissue in order to destroy it. Dielectric and thermal properties influence the deposition of electromagnetic energy and the heat distribution into the tissue, respectively. Accurate knowledge...

Objectives To develop and assess the performance of a system for shared ventilation that uses clinically available components to individualize tidal volumes under a variety of clinically relevant conditions. Design Evaluation and in vitro validation study. Setting Ventilator shortage during the SARS-CoV-2 global pandemic. Participants The design...

Microwave tomography (MWT) can be used as an alternative modality for monitoring human bone health. Studies have found a significant dielectric contrast between healthy and diseased human trabecular bones. A set of diverse bone phantoms were developed based on single-pole Debye parameters of osteoporotic and osteoarthritis human trabecular bones. T...

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia and is associated with significant morbidity and mortality. The autonomic nervous system (ANS) plays an important role in the initiation and development of AF, causing alterations in atrial structure and electrophysiological defects. The intrinsic ANS of the heart consists of mu...

We produced an anatomically and dielectrically realistic phantom of the axillary region to enable the experimental assessment of Axillary Lymph Node (ALN) imaging using microwave imaging technology. We segmented a thoracic Computed Tomography (CT) scan and created a computer-aided designed file containing the anatomical configuration of the axillar...

The dielectric characterization of tissue targets of microwave thermal ablation (MTA) have improved the efficacy and pre-procedural planning of treatment. In some clinical scenarios, the tissue target lies at the interface with an external layer of fat. The aim of this work is to investigate the influence of the dielectric contrast between fat and...

Platelet and fibrin-rich blood clots can respond differently to red blood cell rich clots during ischemic stroke treatment, which includes thrombolysis and mechanical thrombectomy. Currently, there is no accurate way to identify the type of clot in advance of treatment. If the type of blood clot can be identified, the optimum clot removal process c...

Objective: Multi-Frequency Symmetry Difference Electrical Impedance Tomography (MFSD-EIT) can robustly detect and identify unilateral perturbations in symmetric scenes. Here, an investigation is performed to assess if the algorithm can be successfully applied to identify the aetiology of stroke with the aid of machine learning. Methods: Anatomic...

The dielectric properties of biological tissues are typically measured using the open-ended coaxial probe technique, which is based on the assumption that the tissue sample is homogeneous. Therefore, for heterogeneous tissue samples, additional post-measurement sample processing is conducted. Specifically, post-measurement histological analysis may...

Microwave hyperthermia is a promising cancer treatment used in combination with radio- and chemotherapy. Typically, hyperthermia systems involve several antennas that transfer electromagnetic energy into the tissue. The principal need in hyperthermia treatment is to optimally focus the heating into the target while minimising heating in the surroun...

Electromagnetic-based hyperthermic therapies induce a controlled increase of temperature in a specific tissue target in order to increase the tissue perfusion or metabolism, or even to induce cell necrosis. These therapies require accurate knowledge of dielectric and thermal properties to optimise treatment plans. While dielectric properties have b...

The coaxial probe technique is used to acquire the dielectric properties of biological tissues in the microwave frequency range. To dielectrically characterise heterogeneous samples, the sensing radius of the probe must be known. Thus, in this study, for the first time, both experimental and numerical investigations were conducted to analyse and mo...

Many clinical investigations of microwave breast imaging systems are ongoing. However, few studies have investigated the optimal antenna design to maximise imaging performance. In this paper, the impact of the radial behaviour of the antenna on coverage area is investigated. A simplified antenna model in a homogeneous medium is used to estimate the...

In electromagnetic hyperthermic applications, the thermal properties of the biological tissue under treatment, as well as its dielectric properties, influence the deposition of the electromagnetic energy and the heat distribution into the tissue. Thus, their knowledge can allow to accurately model the therapeutic results. The induced heat distribut...

Purpose The assessment of the size and shape of breast tumors is of utter importance to the correct diagnosis and staging of breast cancer. In this paper, we classify breast tumor models of varying sizes and shapes using signals collected with a monostatic ultra‐wideband radar microwave imaging prototype system with machine learning algorithms spec...